At 5 months I would guess CottN is a pullet too then since from the one picture it looks like very little comb development. I don't know about the others (are they turkens?) I would think any roo at 5 months would have much ore comb development
With the BR - the pullets also usually have a dark wash down the legs and the cockrels have more yellow legs. So I think with the darker feathers, the dark wash down the legs, and the not terribly huge comb development - you can probably be pretty confident of that one.
If you can get a better picture of CottN's head and let us know what breed we might be able to help more.